This paper proposes a novel method for digital image watermarking, in which watermarks are embedded in the domain of fast para-metric transforms based on known spread spectrum approaches. Fast parametric transforms have the ability to adapt the forms of base vectors, which enables automatic selection of the domain of watermarking in relation to the pair: a marked image – a watermarking attack. The process of adapting the forms of fast parametric transforms is carried out with aid of the classical genetic algorithm with the fitting function based on the known measure of separability of watermarks. The effectiveness of the proposed method has been verified experimentally on the basis of the images of two classes, i.e. natural images and technical diagrams. The results taking into account both the efficiency of watermark embedding and the generated distortions in the marked images are summarized in tables and accompanied by an appropriate commentary.
In this study a two-step short wet etching was implemented for the black silicon formation. The proposed structure consists of two steps. The first step: wet acidic etched pits-like morphology with a quite new solution of lowering the texturization temperature and second step: wires structure obtained by a metal assisted etching (MAE). The temperature of the process was chosen due to surface development control and surface defects limitation during texturing process. This allowed to maintain better minority carrier lifetime compared to etching in ambient temperature. On the top of the acidic texture the wires were formed with optimized height of 350 nm. The effective reflectance of presented black silicon structure in the wavelength range of 300-1100 nm was equal to 3.65%.